I've recently upgraded to xorg-x11 1.6 (it is shipped with several up-to-date Linux distributions like OpenSuSe 11.2) and encountered a problem with my keyboard. All keypresses repeated twice, which made impossible to use xorg-server. After looking through /var/log/Xorg.0.log I found that somehow Xserver decided to add my keyboard twice. So all events from the keyboard were processed two times. I fixed this problem by adding this line to xorg.conf into Section "ServerFlags" block
Option "AutoAddDevices" "off"